This invention relates to equipment for processing of liquids used in products for human consumption, e.g., dairy products such as milk, cream, and ice cream mix, other liquid food products, e.g., fruit juices and soups, or pharmaceuticals. The invention is more particularly concerned with sanitary valves of the type used in the dairy, food processing, and/or pharmaceutical industries, in which the flow of a fluid is to be regulated or diverted from one flow path to another. The invention is also concerned with diaphragm valves, that is, valves of the type in which a flexible membrane conforms to a fluid port, when pressed against the port, to limit, restrict, or block the flow of the fluid. The invention is more specifically concerned with a diaphragm valve of simple design and which can be cleaned and sterilized in place by the flow of a cleaning liquid through the valve. Sanitary diaphragm valves of this type can be used in a milk pasteurization line as a bypass valve or as a pressure regulating valve.
Pasteurization of milk and other processes for heat treating milk or other food or ingestible products are required to conform to published standards of the U.S. Public Health Service, and there are similar regulations concerning equipment for processing other products. By law, the milk or other product has to be heated to certain temperatures and held at a particular temperature. The pressures and pressure differentials of the product have to be closely monitored at certain points in the process. This means that accurate pressure regulating valves have to be present in the conduit, and must be replaced whenever they fail. Diversion valves are also required to divert the milk or other liquid food product from a continuous flow pasteurization path to another path in the event that the process needs to be interrupted or if a problem develops in the line. On the other hand, in order to ensure that the sanitary conduit can be cleansed and sanitized between processes, the conduit, including any diversion valves and pressure regulating valves, need to be designed so that it can be completely cleaned in place of any milk or other product by washing it and rinsing it with a cleaning fluid that must reach every point on the interior of the conduit, including every point in the valve cavities. No threaded connectors can be used anywhere that the liquid product flows, because of the difficulty in cleaning the threads. In order to accommodate this requirement, the sanitary valves used in the dairy industry and other food processing industries have been complex and difficult to repair and maintain, and represent a significant capital expense.
An example of a diaphragm valve is described in Hughes U.S. Pat. No. 2,577,967. That valve is a differential type diaphragm valve, and is controlled by pressure in an air line. The closure force of the valve is the resultant of the difference in pressure in the space above the diaphragms and in the space between the diaphragms. A diaphragm based poppet valve, as used in the chemical processing industry, is described in Leys U.S. Pat. No. 7,063,304. Diaphragm valves can also be used as pilot valves in the context of a pneumatic volume booster, e.g., Lafler et al. U.S. Pat. No. 6,668,848.
A sanitary diaphragm valve is described in Browne et al. U.S. Pat. No. 7,364,132. That particular valve has a cone shaped actuator, and a bowl or dome-shaped housing with a hemispherical valve cavity. That valve requires complex internal surfaces to permit the inside of the sanitary valve to be cleansed and sterilized.